10. Is there any way to mitigate the consequences of tsunamis?

One of the cornerstones of tsunami mitigation is hazard assessment: through this process, vulnerable coastal areas are mapped and the potential risk for people living there is identified.

The value of information was dramatically illustrated during the Indian Ocean tsunami. Most victims received no warning – but thousands of lives were saved in cases where tsunami knowledge existed and was used.

Experts have argued that tsunami warning systems need to be underpinned by public awareness campaigns and emergency response plans if they are to be effective.

Warnings are of little use if people do not know how to respond to them. Knowledge becomes even more critical if warning times are short – or there is no warning at all – in which case people must know how to react immediately.

The value of indigenous knowledge was highlighted by Simuelue islanders (Indonesia), who lost only seven of their 78,000 inhabitants even though the 2004 tsunami struck them just eight minutes after the earthquake. They have kept alive, through oral history, the lessons of a tsunami that struck in 1907 (known as “smong”): Simuelue islanders knew exactly what to do when the tsunami happened while populations of other nearby coastal areas were decimated.

A tsunami mitigation plan needs to:

  • Quickly confirm potentially destructive tsunamis and reduce false alarms.
  • Address local tsunami mitigation and the needs of coastal residents.
  • Improve coordination and exchange of information to better utilize existing resources.
  • Sustain support at state and local level for long-term tsunami hazard. 
  • Improve the awareness and preparedness of communities for tsunamis:
    • Raise the awareness of affected populations.
    • Supply tsunami evacuation maps.
    • Improve tsunami warning systems.
    • Incorporate tsunami planning into state and federal all-hazards mitigation programmes.

Civil defence authorities in each country can initiate public education programme consisting of seminars and workshops for responsible government officials, can publish informational booklets on the hazards of tsunami, and can co-ordinate with the communications media on the announcement of tsunami information. Other government agencies can take action also to mitigate future losses from tsunami. For example, government agencies can develop sound coastal management policies, which include zoning and planning for tsunami-prone coastal areas.

Internally, government agencies can streamline and co-ordinate their operating procedures and communications so they can perform efficiently when the tsunami threat arises. Procedures related to tsunami warnings should be reviewed frequently to define and determine better respective responsibilities between the different government agencies at all levels.

Scientific organizations can undertake research and engineering studies in developing evacuation zones or engineering guidelines for building coastal structures. Audio-visual materials can be prepared for educating children in schools and the public in general. Brochures and pamphlets can be printed describing the tsunami warning system and what the public can do in time of tsunami warning.

The natural environment can provide protection against tsunamis, and environmental destruction to make way for development can raise the tsunami risk of coastal communities. Tropical coastal ecosystems have sophisticated natural insurance mechanisms to help them survive the storm waves of typhoons and tsunamis such as coral reefs being equivalent of natural breakwaters causing waves to break offshore and allowing them to dissipate most of their destructive energy before reaching the shore.

Mangrove forests also act as natural shock absorbers, “soaking up destructive wave energy and buffering against erosion”. Systems of marshes, tidal inlets and mangrove channels also help limit the extent of inundation by floodwaters and enable flood waters to drain quickly.

Places that had healthy coral reefs and intact mangroves were far less badly hit than places where the reefs had been damaged and the mangroves ripped out and replaced by beachfront hotels and prawn farms during 2004 Tsunami.

However, there has been widespread destruction of natural coastal habitats to make way for urban development, population growth, industry, aquaculture, agriculture and tourism.

The World Wildlife Fund (WWF, http://www.worldwildlife.org) has recommended that tsunami mitigation strategies take into account:

  • Rehabilitation and restoration of degraded coastal ecosystems that help protect from storm waves, especially coastal marshes and forests, mangroves and coral reefs.
  • Adoption of integrated coastal zone management, including zoning and mandatory coastal setback. For example, hotels should not be built within a safety zone from the high tide mark.
  • Strict enforcement of land and coastal-use planning and policies, including natural disaster risk assessments.
  • Implementation of incentives to ensure that sensitive facilities are built away from high risk areas.
  • Risk assessment that helps reduce the vulnerability of coastal development.